Simple Strategies for Minimization of Cooling Water Usage in Binary Power Plants

Abstract

The geothermal resources which could be used for the production of electrical power in the United States are located for the most part in the semi arid western regions of the country. The availability of ground or surface water in the quantity or quality desired for a conventional "wet" heat reinjection system represents a barrier to the development of these resources with the binary cycle technology. This paper investigates some simple strategies to minimize the cooling water usage of binary power plants. The cooling water usage is reduced by increasing the thermal efficiently of the plant. Three method of accomplishing this are considered here: by increasing the average source temperature, by increasing the geofluid outlet temperature; decreasing pinch points on the heat reinjection heat exchangers, increasing their size; and using internal recuperation within the cycle. In addition to the impact on water usage, the impact on cost of electricity is determined. The paper shows that some of these strategies can reduce the cooling water requirements 20 to 30 % over that for a plant similar to the Heber Binary Power Plant, with a net reduction in the cost of electricity of about 15%.